Efflorescence on floor - DPC/DPM breach

[happytimes]

Had some building work done last year include new French doors. Have been saving up some more £££ to finish the room.

This winter I’ve noticed a patch of efflorescence. It didn’t happen last year. Seems a bit odd. Are there any immediate actions I should take?
The second photo is under that grey sheet. The cill of the door on the outside is a full brick height higher than the gravel perimeter of the patio.
Added some other photos of the renovation.

Someone told me that CLS bit of wood shouldn't have been put under the doors and I should replace it with a row of engineering bricks. I'll definitely do that but I'm not sure how that will solve the issue. If moisture is coming through the floor that'll keep happening now matter. In construction I've seen that the DPM comes up and over the inner layer of block work and the DCP sits on the exterior layer. I've looked back at build photos and can see the DPC but there's no way the builder could have extended the existing DPM. Not even sure why they put that big piece of membrane in there now.

Can anybody shed any light on what I should do?

One possible solution - There’s a step of 7cm down into that room so was thinking of using that to my advantage and put in an in-screed UFH. (Will be hiring a pro to do that). I could ‘tank’ the floor or something just before doing the UFH - or is that likely overkill?

thank u for any advice!

 

[Mr Chibs]

When you lifted up the grey sheet, was there any moisture on the back of the sheet?

Is there a cavity between the wood and the outside brickwork skin?
Brick would have been a better choice to me.

Would guess the reason the large flap of grey/black DPC is to stop damp reaching your screed floor (when you get it).
The concrete slab looks to be right up to the outside skin, there is no DPM visible, can't imagine there isn't one! but if not, then moisture from outside can be wicked inside.

Is the outside brick skin sat on the slab?

Can you take a pic from outside looking at the doors please.

 

[happytimes]

hi! Firstly, thank u for taking the time to respond.

There’s no visible moisture under that DPC. However I would say that wood CLS is damp feeling. I don’t know if there’s a cavity between it and the outer skin.

From the photos I have I think the old white sliding doors were sitting directly on the slab. There was no outer brick layer. I remember discussing with the builder that they were putting in that brick level to avoid damp issues. The outer layer of yellow brick that the new doors sit on is definitely set on the slab.

I’ve attached a couple of old photos from before the renovation (white doors). Also a couple of now (black doors) when the garden was being done.

Do you think the DPC for that layer should have been placed 1 row down directly on top of the slab instead of on the brick row?

I still can’t wrap my head around how to seal it all up. At the time the builder was unaware that I was going to raise the floor with a screed. He thought it was just being recarpeted. So I’m not entirely sure what he was expecting me to do with that DPC.

Thanks again!

 

[happytimes]

When you lifted up the grey sheet, was there any moisture on the back of the sheet?

Is there a cavity between the wood and the outside brickwork skin?
Brick would have been a better choice to me.

Would guess the reason the large flap of grey/black DPC is to stop damp reaching your screed floor (when you get it).
The concrete slab looks to be right up to the outside skin, there is no DPM visible, can't imagine there isn't one! but if not, then moisture from outside can be wicked inside.

Is the outside brick skin sat on the slab?

Can you take a pic from outside looking at the doors please.

Just adding another few photos of after the gravel was placed in between the pavers. I can take a much closer one in daylight tomorrow. Thanks

 

[^woody^]

Looks like you've had water penetration from under the frame after heavy rain - either the joint below the cill or that course of bricks has no DPM between the wall and the screed/floor slab

 

[foxhole]

Had some building work done last year include new French doors. Have been saving up some more £££ to finish the room.

This winter I’ve noticed a patch of efflorescence. It didn’t happen last year. Seems a bit odd. Are there any immediate actions I should take?
The second photo is under that grey sheet. The cill of the door on the outside is a full brick height higher than the gravel perimeter of the patio.
Added some other photos of the renovation.

Someone told me that CLS bit of wood shouldn't have been put under the doors and I should replace it with a row of engineering bricks. I'll definitely do that but I'm not sure how that will solve the issue. If moisture is coming through the floor that'll keep happening now matter. In construction I've seen that the DPM comes up and over the inner layer of block work and the DCP sits on the exterior layer. I've looked back at build photos and can see the DPC but there's no way the builder could have extended the existing DPM. Not even sure why they put that big piece of membrane in there now.

Can anybody shed any light on what I should do?

One possible solution - There’s a step of 7cm down into that room so was thinking of using that to my advantage and put in an in-screed UFH. (Will be hiring a pro to do that). I could ‘tank’ the floor or something just before doing the UFH - or is that likely overkill?

thank u for any advice!

Engineering bricks don’t swell and absorb water and rot, timber does.

 

[happytimes]

Morning - The replies are really appreciated.

This morning I took a photo of the outside wall. The DPC is on top of the ground level of brick. I've attached a diagram of how I think it's been constructed.

From the advice I'm hearing about using engineering bricks - is the diagram on the right accurate? It still feels to me that there's no barrier to stop moisture coming up or in from the outside.

Thanks again

 

[^woody^]

 

[happytimes]

View attachment 286325

Thanks for explaining @^woody^. That’s really helpful and I understand why it’s happening now.

What do you reckon my options are now? Cheers!

 

[^woody^]

Your drawing indicates the floor slab going to the outside. Is that correct?

Where is the DPM? What's the arrangement at the threshold?

It may be relatively simple to remedy, but knowing the DPM arrangement is crucial.

 

[Mr Chibs]

What about perimeter upstand insulation, 50mm celotex strip glued to the engineering brick, then when you screed, fill up to the height of the insulation. You will then need perimeter foam insulation for your UFH.

 

[foxhole]

Exterior level should ideally be two bricks below dpc, yours looks high in photo .

 

[happytimes]

Your drawing indicates the floor slab going to the outside. Is that correct?

Where is the DPM? What's the arrangement at the threshold?

It may be relatively simple to remedy, but knowing the DPM arrangement is crucial.

Afternoon @^woody^ . I've gone back through my photos again and yes you're right to question the slab.
I found a photo of that window area just after they were removed and the extension foundations were being dug.

I've pieced together a better diagram of what think it is and labelled a few elements for clarity before and during the build.

Based on the early photo I have it seems like the slab comes right up to the outer layer of bricks (though can't be sure) and I can see evidence of a DPM coming up from the ground there - but certainly not enough to overlap an inner layer of brick). I assume it's around the whole perimeter. There doesn't seem to be a cavity either (could just be hidden). There's 2 layers of yellow brick underground and then engineering bricks beneath.

Does this shed any light on a solution? Panicking this is gonna cost the earth to fix. :-/

As I'd mentioned earlier - there is a 7cm step down into that room. There was a small step already and that was made greater by the fact the adjoining room has retrofit UFH. So, when I come to put in the UFH in-screed, I could put down a whole new DPM, 10mm of insulation as recommended by the UFH company, and then 50mm of screed. Overkill? Not a solution?

Cheers

 

[Mr Chibs]

Is there any insulation under the current slab? I'm guessing not... really it wanted either or cavity or insulating it from the outside brick skin.

As for UFH, you would need to go something like 100mm of PIR above the slab, then 55-75mm of screed to embed the pipes (I have this spec) total 155-175mm, so you are short already.

Liquid screeds can go thinner but wouldn't think less than 45mm. With insufficient insulation, you will be wasting heat...that leaches through the insulation and into the concrete slab. Ideally you want to slow this down, with as thick as you can fit, insulation.

 

[happytimes]

Is there any insulation under the current slab? I'm guessing not... really it wanted either or cavity or insulating it from the outside brick skin.

As for UFH, you would need to go something like 100mm of PIR above the slab, then 55-75mm of screed to embed the pipes (I have this spec) total 155-175mm, so you are short already.

Liquid screeds can go thinner but wouldn't think less than 45mm. With insufficient insulation, you will be wasting heat...that leaches through the insulation and into the concrete slab. Ideally you want to slow this down, with as thick as you can fit, insulation.

I looked on the planning portal and that extension was registered in 2011... The exterior has air bricks which indicates a beam and block floor; so I'd say there would be insulation in that case? The UFH guy did ask me all this before he committed to quoting for an in-screed system. He seemed pretty decent. All this isn't going to start until spring next year when I've saved the £££.

I guess it's just that new layer of brick (that's above the slab level) is basically allowing water to come in... had the cill been set on ground level it wouldn't happen?? How to fix it though? Wondering if a drainage channel along the outside help.